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Darwin-L Message Log 2:35 (October 1993)

Academic Discussion on the History and Theory of the Historical Sciences

This is one message from the Archives of Darwin-L (1993–1997), a professional discussion group on the history and theory of the historical sciences.

Note: Additional publications on evolution and the historical sciences by the Darwin-L list owner are available on SSRN.


<2:35>From DARWIN@iris.uncg.edu  Fri Oct  8 11:35:02 1993

Date: Fri, 08 Oct 1993 12:41:55 -0400 (EDT)
From: DARWIN@iris.uncg.edu
Subject: Ploidy and polymorphism in evolution and philology
To: darwin-l@ukanaix.cc.ukans.edu
Organization: University of NC at Greensboro

Let me add another case to the discussion of ploidy and polymorphism in
language and evolution, namely, the case of textual transmission.  I'm not
quite able to fit all of these examples into a precisely defined framework
yet, but exploring the parallels is very illuminating I think.  (William
Whewell would be proud of us: "It is not an arbitrary and useless
proceeding to construct such a Class of [historical] sciences.  For wide
and various as their subjects are, it will be found that they have all
certain principles, maxims, and rules of procedure in common; and thus may
reflect light upon each other by being treated together.")

The discussion began with Jeff Wills' example of someone who speaks two
languages, and how these will influence one another in that speaker, even
though the languages themselves are different "tips" of the linguistic
tree.  Further, the same individual will use different languages or
different speech registers in different environmental contexts.

Several interesting evolutionary (biological) parallels were developed,
including the fact that in many organisms (such as ourselves) genetic
material is carried both in the nucleus and in extranuclear organelles such
as mitochondria and chloroplasts, and that these different genomes may
influence one another, although they function semi-autonomously and have
different rules of transmission.  Another parallel that was suggested was
the differential expression of different genes at different times in
development: all of them are present at all times, but they may be "turned
on" at different times in different circumstances.  This last case seems
somewhat like the use of different speech registers in different contexts.

To set up the case of textual transmission, let's consider first the
arrangement of nuclear genes on chromosomes in a bit more detail.  As was
mentioned, the majority of macroscopic organisms are said to be "diploid",
that is, they have two copies of each chromosome.  At any particular
corresponding point (locus) the two chromosomes may be identical, or they
may differ.  If they differ the individual is said to be "polymorphic" at
that locus: its two matching chromosomes have different readings at that
particular locus.  It might be the case that some particular individual is
not polymorphic, but that its population is -- the individual's chromosomes
match at that point, but there are other individuals in the population that
have different readings at that chromosomal location.  I have been speaking
in genetic terms here, but much the same can be said of morphology also: a
population of organisms might be polymorphic for a particular eye color,
with some individuals brown, some blue, some green, as is the case in
humans.  And it is possible for one individual to be morphologically
polymorphic if we consider its left and right sides (doesn't happen very
often with eye color in humans, but can in other things).

Now the new case I want to interject is the case of textual transmission.
While my own background is in evolutionary biology, I've been working with
a textual scholar on some of these problems so have at least a basic idea
of what's going on, although specialists are welcome to amplify or correct
what I say, of course.  The works of most medieval and ancient authors are
not known today from copies actually written by the authors themselves.
What we have are copies of the originals, and copies of copies, written
over hundreds or thousands of years.  Because the process of copying is
imperfect, the many extant copies of a work will ordinarily differ from one
another at many locations (loci!).  But the interesting point with regard
to the present discussion is that a single manuscript may be polymorphic at
one or more loci.  If a scribe making a copy of a text comes across a word
that doesn't seem to make sense, the scribe may copy the word but write
above it or in the margin another word that he thinks is in fact the
correct reading.  Or the scribe might insert what he thinks is the correct
reading into the main text and put the old and perhaps erroneous reading
between the lines or in the margin.  Thus at that particular locus the one
physical document will be polymorphic: it will carry more than one reading.
Unlike organisms, however, manuscripts aren't of any particular ploidy;
rather, at most loci a manuscript will carry only one reading (haploid), at
some loci it will carry two readings (diploid), and at some loci it might
carry three or more readings (triploid or polyploid).

There are many differences between manuscript transmission and both
linguistic and biological evolution, most notably that manuscript
transmission is not a populational phenomenon (it is closer to being
clonal, with a fair bit of horizontal transmission), but I will leave those
issues for a later discussion so as to emphasize the particular issue of
ploidy/polymorphism.

The best general introduction to manuscript transmission for evolutionary
biologists is Cameron's paper in the Hoenigswald & Wiener volume that I
have mentioned here before.  The full citation is:

Cameron, H. Don.  1987.  The upside-down cladogram: problems in manuscript
affiliation.  Pp. 227-242 in: Biological Metaphor and Cladistic
Classification: An Interdisciplinary Perspective (Henry M. Hoenigswald &
Linda F. Wiener, eds.).  Philadelphia: University of Pennsylvania Press.

Bob O'Hara, Darwin-L list owner

Robert J. O'Hara (darwin@iris.uncg.edu)
Center for Critical Inquiry and Department of Biology
100 Foust Building, University of North Carolina at Greensboro
Greensboro, North Carolina 27412 U.S.A.

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